Refer the issue for making mixin transformation modular.

pkg/front_end/lib/src/incremental_kernel_generator_impl.dart

Index: pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
diff --git a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
index 644289d9489eeb515c882c53f574512ba869e7e1..b78ac35fb1de46a5c65c5cd551266042d1ea5ec6 100644
--- a/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
+++ b/pkg/front_end/lib/src/incremental_kernel_generator_impl.dart
@@ -329,7 +329,8 @@ class IncrementalKernelGeneratorImpl implements IncrementalKernelGenerator {
     for (var file in transitiveFiles) {
       signatureBuilder.addString(file.uri.toString());
       // TODO(scheglov): Stop using content hashes here, when Kernel stops
-      // copying methods of mixed-in classes,
+      // copying methods of mixed-in classes.
+      // https://github.com/dart-lang/sdk/issues/29881
       if (hasMixinApplication) {
         signatureBuilder.addBytes(file.contentHash);
       } else {